Linear flow-velocity gradient chromatography-An efficient method for increasing the process efficiency of batch and continuous capture chromatography of proteins.

A new method was proposed for increasing the capture chromatography process efficiency, linear flow-velocity gradient (LFG). The method uses a linear decreasing flow-velocity gradient with time during the sample loading. The initial flow velocity, the final flow velocity and the gradient time are the parameters to be tuned. We have developed a method for determining these parameters by using the total column capacity and the total loaded amount as a function of time. The capacity can be calculated by using the relationships between dynamic binding capacity (DBC) and residence time. By leveraging the capacity, loading amount, and the required conditions, the optimum LFG can be designed. The method was verified by ion-exchange and protein A chromatography of monoclonal antibodies (mAbs). A two-fold increase in the productivity during the sample loading was possible by LFG compared with the constant flow-velocity (CF) operation. LFG was also applied to a 4-column continuous process. The simulation showed that the cost of resin per unit amount of processed mAbs can be reduced by 13% while 1.4 times enhancement in productivity was preserved after optimization by LFG compared to CF. The process efficiency improvement is more pronounced when the isotherm is highly favorable and the loading volume is large.

Morphological variation of two taxonomically distant plant species along a natural flow velocity gradient.

• The similarity of morphological plastic response to physical stress has been poorly tested among distant plant taxons as yet. • The effect of flow stress was compared for two species -Berula erecta and Mentha aquatica- through 14 morphological traits measured for five sets of 30 individuals in five patches organised along a natural velocity gradient. Size-dependent and size-corrected traits were analysed by single correlations and multivariate analyses. • B. erecta exhibited the expected pattern, that is a sharp decrease of all but one size-dependent trait as velocity increased. Five and four size-corrected traits were correlated with velocity, for B. erecta and M. aquatica, respectively, but three of them showed an opposite trend for the two species. Within-patch trait variability, as hypothesized, tended to decrease with velocity for B. erecta. • The two species exhibited partly opposite responses despite the involvement of common traits. Small size allowed B. erecta to escape flow stress, whereas M. aquatica acquired a more streamlined morphology. The adaptive value of these morphological adjustments should be assessed through drag measurements.